A new method for breath-to-breath determination of oxygen flux across the alveolar membrane

A new method for breath-to-breath determination of the oxygen flux across the alveolar membrane is described. The principle of the method is to integrate the product of oxygen concentration and flow in the respiratory gas over an interval, which covers a complete respiratory cycle. The result is corrected for the change in oxygen content of the lungs through a formula, which, in contrast to those used in other methods, is independent of the residual capacity of the lungs. The method was evaluated with respect to repeatability by repetitive measurement of oxygen flux in twenty volunteer subjects, and with respect to accuracy by comparing the measured oxygen fluxes with those obtained by the gas collection method. The coefficient of variation was found to be 8% and the breath to breath determinations were, on an average, 6% lower than those of the gas collection method.